This invention relates to an automotive body paint booth, and particularly to an air flow control system for such a paint booth.
Typically automotive bodies are painted in the factory by placing each automotive body on a conveyor, and moving the conveyor through an elongated booth, or tunnel, containing multiple contiguous chambers. In each chamber a specific operation is performed on an automotive body as it passes through the respective chamber.
In some chambers mechanical robot painting mechanisms apply paint colorant or clear coat to specific areas of the automotive body, using electrostatic coating techniques. In other chambers, paint colorant or clear coat is applied mechanically to the automotive body, using compressed air spraying techniques. In some chambers a human technician is employed to spray paint colorant or clear coat to areas of the automotive body that cannot be adequately covered by the use of mechanical coating sprayers. The paint spray booth includes at least one flash-off chamber designed to remove volatile paint solvents that give the paint colorant or clear coat flowability; removal of such volatiles prevents different colorants from running or mixing together on the automotive body.
In many of the spray booth chambers excess paint mists or airborne particulates are generated as a result of the coating processes performed in the respective chambers. To remove such mists and airborne particulates it is a common practice to provide a down flow air system in the affected chambers. Air flows downwardly through a perforated ceiling, into the chamber, and through a perforated floor into a sub-chamber containing a mist eliminator mechanism. The down flowing air continually removes airborne particulates in the chamber that could adversely affect the quality of the coating operation or pose a health risk to the human technician in the chamber.
One problem associated with the down flowing air is that any unbalance in the down flow air velocity in contiguous chambers can produce an undesired horizontal cross flow from one chamber to an adjacent chamber. Air tends to migrate horizontally from a chamber having a relatively high velocity down flow into a contiguous chamber having a lower velocity down flow. If such cross flows are left uncontrolled the associated particulate migrations can adversely affect the coating process or produce uncomfortable conditions for the human technicians. For example, the introduction of paint particles of one color into a chamber used for applying a different colorant to the automotive body can adversely affect product quality.
The present invention is concerned with an airflow control system, wherein horizontal cross flows between contiguous chambers in the paint spray booth are controlled so as to prevent undesired product quality problems or adverse conditions for the human technicians in selected chambers. The airflow control system includes sensors for measuring the down flow velocity in each affected chamber, and also the cross flow velocity between contiguous chambers. Signals generated by the velocity measurement sensors are applied to control motors used on air supply fans and dampers that determine the down flow velocity values in the contiguous chambers.
In the present invention, the cross flows between contiguous chambers are controlled by adjusting the down flow velocities in the contiguous chambers. An airflow control algorithm, containing target values for down flow and cross flow, provide a base against which the sensed velocity values are compared, so as to provide a desired air flow balance.
Specific features of the invention will be apparent from the attached drawing and description of an illustrative embodiment of the invention.